I've never had to send more than an email.
> Hey Frank, just read through the non-compete and I have a few small changes. 1. Since we're only working on a proto-type for a classifier for sorting documents can we amend the non-compete to specifically mention that domain? I don't want to limit my options unnecessarily but I appreciate you wanting to stop me from turning around and selling this stuff to Microsoft once you're done. 2. The term is unlimited right now, which I'm not even sure if that can stand up in court. Let's cap it at 2 years from project completion or my leaving the project. If it's easier for you to just agree to these changes over email just reply by saying "Sure Zach, these changes are completely reasonable." and I'll sign and add "with agreed changes" next to my signature.
That will 100% stand up in court, and really if they say "no" to it then you say "no" to the opportunity, but I've never not been able to get to an agreement with someone. Good help is hard to find, and a little charisma goes a long way when negotiating.